As disclosed in Patent Document 1, a water flow power generator which generates electric power by using an ocean current and a water flow in seas or rivers includes a vane wheel and a power generator. The vane wheel has a plurality of blades (vanes) extending toward an outer peripheral side. In the power generator, an end portion of a rotating shaft is connected to the vane wheel, and the rotating shaft is rotated together with the vane wheel rotated by the ocean current and the water flow, thereby generating electric power.
This underwater power generator includes a brake mechanism in order to stop the rotation of the vane wheel during maintenance work.